Make AverageLag count scroll prediction change

AverageLag are calculated from latency_info.scroll_update_delta.
It was set from GestureScrollUpdate event's delta_y; however, scroll
prediction is done after scroll_update_delta set, which means the
AverageLag did not count in the prediction result.

This CL adds setting the scroll_update_delta from GSU, so it will
count in the prediction change as well.

Bug: 836352
Change-Id: I979e0da617dbfdfa6735aee33958cb9dac9b8331
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1509102Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Commit-Queue: Ella Ge <eirage@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638732}

ui/events/blink/input_handler_proxy.cc

@@ -261,6 +261,14 @@ void InputHandlerProxy::DispatchSingleInputEvent(
     std::unique_ptr<EventWithCallback> event_with_callback,
     const base::TimeTicks now) {
   ui::LatencyInfo monitored_latency_info = event_with_callback->latency_info();
+
+  if (event_with_callback->event().GetType() ==
+      WebInputEvent::kGestureScrollUpdate) {
+    monitored_latency_info.set_scroll_update_delta(
+        static_cast<const WebGestureEvent&>(event_with_callback->event())
+            .data.scroll_update.delta_y);
+  }
+
   std::unique_ptr<cc::SwapPromiseMonitor> latency_info_swap_promise_monitor =
       input_handler_->CreateLatencyInfoSwapPromiseMonitor(
           &monitored_latency_info);

ui/events/blink/input_handler_proxy_unittest.cc

@@ -1916,6 +1916,67 @@ TEST_F(InputHandlerProxyEventQueueTest, ScrollPredictorTest) {
   testing::Mock::VerifyAndClearExpectations(&mock_input_handler_);
 }
 
+TEST_F(InputHandlerProxyEventQueueTest, LatencyInfoScrollUpdateDelta) {
+  // Scroll on compositor.
+  cc::InputHandlerScrollResult scroll_result_did_scroll_;
+  scroll_result_did_scroll_.did_scroll = true;
+
+  EXPECT_CALL(mock_input_handler_, ScrollBegin(testing::_, testing::_))
+      .WillOnce(testing::Return(kImplThreadScrollState));
+  EXPECT_CALL(mock_input_handler_, SetNeedsAnimateInput()).Times(1);
+  EXPECT_CALL(
+      mock_input_handler_,
+      ScrollBy(testing::Property(&cc::ScrollState::delta_y, testing::Gt(0))))
+      .WillOnce(testing::Return(scroll_result_did_scroll_));
+  EXPECT_CALL(mock_input_handler_, ScrollEnd(testing::_, true));
+
+  HandleGestureEvent(WebInputEvent::kGestureScrollBegin);
+  HandleGestureEvent(WebInputEvent::kGestureScrollUpdate, -20);
+  HandleGestureEvent(WebInputEvent::kGestureScrollUpdate, -40);
+  HandleGestureEvent(WebInputEvent::kGestureScrollEnd);
+  input_handler_proxy_->DeliverInputForBeginFrame();
+
+  EXPECT_EQ(0ul, event_queue().size());
+  // Should run callbacks for every original events.
+  EXPECT_EQ(4ul, event_disposition_recorder_.size());
+  EXPECT_EQ(4ul, latency_info_recorder_.size());
+  EXPECT_EQ(false, latency_info_recorder_[1].coalesced());
+  EXPECT_EQ(-60, latency_info_recorder_[1].scroll_update_delta());
+
+  EXPECT_EQ(true, latency_info_recorder_[2].coalesced());
+  EXPECT_EQ(-60, latency_info_recorder_[2].scroll_update_delta());
+
+  testing::Mock::VerifyAndClearExpectations(&mock_input_handler_);
+
+  latency_info_recorder_.clear();
+
+  // Scroll on main thread.
+  cc::InputHandlerScrollResult scroll_result_did_not_scroll_;
+  scroll_result_did_not_scroll_.did_scroll = false;
+  EXPECT_CALL(mock_input_handler_, ScrollBegin(testing::_, testing::_))
+      .WillOnce(testing::Return(kMainThreadScrollState));
+  EXPECT_CALL(mock_input_handler_, ScrollEnd(testing::_, true));
+
+  HandleGestureEvent(WebInputEvent::kGestureScrollBegin);
+  HandleGestureEvent(WebInputEvent::kGestureScrollUpdate, -20);
+  HandleGestureEvent(WebInputEvent::kGestureScrollUpdate, -40);
+  HandleGestureEvent(WebInputEvent::kGestureScrollEnd);
+  input_handler_proxy_->DeliverInputForBeginFrame();
+
+  EXPECT_EQ(0ul, event_queue().size());
+  // Should run callbacks for every original events.
+  EXPECT_EQ(8ul, event_disposition_recorder_.size());
+  EXPECT_EQ(4ul, latency_info_recorder_.size());
+
+  EXPECT_EQ(false, latency_info_recorder_[1].coalesced());
+  EXPECT_EQ(-20, latency_info_recorder_[1].scroll_update_delta());
+
+  EXPECT_EQ(false, latency_info_recorder_[2].coalesced());
+  EXPECT_EQ(-40, latency_info_recorder_[2].scroll_update_delta());
+
+  testing::Mock::VerifyAndClearExpectations(&mock_input_handler_);
+}
+
 class InputHandlerProxyMainThreadScrollingReasonTest
     : public InputHandlerProxyTest {
  public: